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SUMMARY:Nadia Bihari Padhan\, Axel Voigt
DTSTART:20261021T070000Z
DTEND:20261021T080000Z
DTSTAMP:20261024T105616Z
UID:MathMAC/66
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/MathMAC/66/"
 >Odd capillarity in two-phase flows\, Generalized Navier-Stokes equation a
 nd asymmetric two-phase flows</a>\nby Nadia Bihari Padhan\, Axel Voigt as 
 part of Modelling of materials - theory\, model reduction and efficient nu
 merical methods (UNCE MathMAC)\n\n\nAbstract\n<b>Odd capillarity in two-ph
 ase flows</b><br>\nFluid interfaces are remarkably rich. A broad range of 
 two-phase and multiphase phenomena can be described within the Cahn–Hill
 iard–Navier–Stokes (CHNS) framework\, where the Navier–Stokes equati
 ons are coupled to the Cahn–Hilliard dynamics through the Korteweg stres
 s associated with interfacial tension. Active two-phase flows\, described 
 for example by active CHNS models\, extend this picture by allowing the me
 chanical interfacial tension to differ from its passive counterpart and ev
 en become negative\, leading to phenomena such as interrupted coarsening a
 nd self-generated flows. In both passive and active formulations\, however
 \, the interfacial stress preserves parity symmetry.  This leads us to ask
  a simple question: what changes when parity symmetry is broken at a fluid
  interface? We address this question by introducing an odd contribution to
  the Korteweg stress. In the sharp-interface limit\, this generalizes the 
 classical Young-Laplace law: in addition to the familiar normal capillary 
 traction\, curvature generates a transverse traction along the interface. 
 We refer to this effect as odd capillarity. We then study the resulting dy
 namics numerically within a diffuse-interface formulation. Odd capillarity
  generates circulating flows around droplets\, strongly modifies interfaci
 al morphology and phase separation\, and\, at sufficiently large strength\
 , produces turbulence even at low Reynolds number. These results illustrat
 e how unconventional stresses can qualitatively reshape the dynamics and m
 orphology of two-phase flows.<p>\n\n<b>Generalized Navier-Stokes equation 
 and asymmetric two-phase flows</b><br>\nOne way to consider activity in fl
 ow is realized by the Generalized Navier-Stokes equation. It is used as a 
 model for bacterial suspensions and provides a higher order equation. We i
 ntroduce the model and solve it numerically. We characterize the turbulent
  flow field and identify similarities and difference with classical inerti
 al turbulence. Characterizing the vorticity with respect to its hyperunifo
 rm properties allows for a new measure to distinguish both. In the second 
 part of the talk we extend this model towards a two-phase system\, couplin
 g it with a classical Navier-Stokes equation using a Cahn-Hilliard equatio
 n. The model now describes a coupled active-passive system and could be ca
 lled Cahn-Hilliard-Generalized-Navier-Stokes (CHGNS) equation. We again so
 lve these equations numerically and explore the emerging morphologies. The
 y turn out to be asymmetric. We explain this behaviour and relate it to ot
 her active CHNS models.\n
LOCATION:https://researchseminars.org/talk/MathMAC/66/
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